The main purpose of the core unit is to provide an in vivo model for the growth of chronic myelogenous leukemia (CML) and normal stem/progenitor cells. NOD/scid animals will be used in experiments to investigate the basic biology of CML progenitors and to model potential therapeutic interventions. The core will breed and maintain NOD/scid mice in the Barrier Animal Facility within the Center for Comparative Medicine at Baylor College of Medicine. The facility uses strict standard operating procedures designed to keep all animals specific pathogen free (SPF). Core personnel will perform all experimental manipulations on NOD/scid mice for the individual project investigators. The core personnel will also provide in vitro manipulation of CML and normal hematopoietic progenitors. For example, the core will provide tissue culture for testing purging protocols and for retroviral vector transduction. The core personnel have special interest and expertise in retroviral vector gene marking technology and will implement serial and clone-specific gene marking techniques as required by the individual projects. The core will provide harvested bone marrow cells from transplanted NOD/scid mice and other tissues involved with leukemic disease as required by the individual investigators. The core personnel will coordinate with the flow cytometry and FISH laboratories for analysis of NOD/scid bone marrow cells and tissues.